where modes drop only the attribute its index reads

3 files changed, 7 insertions, 5 deletions

diff --git a/lib/concepts/Mode.ml b/lib/concepts/Mode.ml
index b3031fc..9c5daa9 100644
--- a/lib/concepts/Mode.ml
+++ b/lib/concepts/Mode.ml
@@ -17,5 +17,5 @@ let exhaustible modes bound =
 
 let project attributes = List.filter (fun {bound; _} -> BatSet.String.subset bound attributes)
 
-let given attributes =
-  List.map (fun {bound; yields} -> {bound= BatSet.String.diff bound attributes; yields})
+let given attribute =
+  List.map (fun {bound; yields} -> {bound= BatSet.String.remove attribute bound; yields})
diff --git a/lib/concepts/Mode.mli b/lib/concepts/Mode.mli
index ba1a04a..0518bca 100644
--- a/lib/concepts/Mode.mli
+++ b/lib/concepts/Mode.mli
@@ -13,4 +13,4 @@ val exhaustible : t -> attributes -> bool
 (** the modes still usable when only [attributes] can be bound. *)
 val project : attributes -> t -> t
 
-val given : attributes -> t -> t
+val given : string -> t -> t
diff --git a/lib/evaluators/FOL.ml b/lib/evaluators/FOL.ml
index 1064c74..60cc89f 100644
--- a/lib/evaluators/FOL.ml
+++ b/lib/evaluators/FOL.ml
@@ -171,8 +171,10 @@ let rec modes =
   | Where (plan, binding) -> (
       let* modes = modes plan in
       match plan with
-      | Base relation when Option.is_some (index_for relation binding) ->
-          Ok (Concepts.Mode.given (bound binding) modes)
+      | Base relation -> (
+        match index_for relation binding with
+        | Some (_, attribute) -> Ok (Concepts.Mode.given attribute modes)
+        | None -> Ok modes )
       | _ -> Ok modes )
 
 let project description relation =